Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “image compression”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Impact Damage Tolerance of Composite Laminates with Through-The-Thickness Stitches

The ability of through-the-thickness stitches to contain damage during a low-velocity impact event and increase the residual strength of stitched panels was investigated in this research. The impact response, spread of interlaminar delaminations, dent depth, surface damage, and static residual strength after impact were studied for carbon-epoxy specimens fabricated from HTS40 TohoTenax standard modulus fibers, stitched together with Vectran 1200 denier thread and infused with API 1078 resin after through-the-thickness stitching. Three different stitch patterns were used to explore the ability to arrest impact damage during and after impact. Simply supported boundary conditions were maintained during the impact testing. Non-destructive evaluations were performed using ultrasonic C-scans and X-ray computed tomography (CT) imaging to determine the shape, size, and location of delaminations. Results indicate that while the dynamic response during the impact event was almost the same for the unstitched specimens and all stitch patterns considered, the extent of delamination and the compression strength after impact varied greatly. For both the 60 J and 80 J impact energies, the delamination area was significantly less for the stitched specimens than for the unstitched specimens, but the range of delamination areas among the stitch patterns was much larger for the lower impact energy than for the greater impact energy. Similarly, while the presence of stitching influenced the compression after impact strength, the strength values for all stitch patterns were very similar. These results are a step toward quantifying the influence of through-the-thickness stitching.

Ranatunga, Vipul↗
DOE OSTI2022

Deformation twinning and detwinning in extruded Mg-4Al: In-situ experiment and crystal plasticity simulation

Deformation twinning and detwinning in extruded Mg-4Al were investigated using in-situ SEM-DIC experiments and crystal plasticity finite element (CPFE) simulation. In this study, the in-situ SEM-DIC method was used to provide a unique set of data including twin/detwin characteristics and twin area fraction in addition to strain maps. A statistical analysis of the activation of twin variants and twin area fraction during both twinning and detwinning was conducted. A strong correlation was found between twin growth/shrinkage and the Schmid Factor (SF) for individual twin variants Higher twin SF during loading and unloading led to higher twin growth and shrinkage, respectively. However, after the applied compressive strain was removed, the pattern of the twin area fractions of the residual twin variants versus their nominal SFs did not follow the trend observed at the maximum compressive strain. Using a systematic methodology and an advanced twin/detwin model, the PRISMS-Plasticity CPFE simulation was calibrated using experimentally determined stress versus strain and twin area fraction versus strain information. A comprehensive evaluation of the CPFE model was conducted to determine its ability to capture the statistics of twin variants activation and twin area fraction. CPFE accurately captured the statistical aspects of both twinning and detwinning. Finally, it also predicted the first dominant twin variant for 47.5% of the grains and at least one of the two dominant twin variants for 80% of the grains at maximum compressive strain.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Chemo-Mechanical Instabilities in Lithium Cobalt Oxide at Higher State-Of-Charge in Li-Ion Batteries

Transition metal oxide cathodes are widely used in commercial Li-ion batteries. However, their practical charge capacity is limited due to severe chemo-mechanical instabilities at higher charge voltage, and state-of-charge condition. Here, in situ stress and strain measurements were synchronized to probe mechanical deformations in the lithium cobalt oxide (LCO) cathode via a multi-beam stress sensor and digital image correlation, respectively. In situ mechanical measurements revealed how Li removal from the electrode structure induces deformations on the LCO composite cathodes during cycling. The structure and morphology of the LCO cathodes were further investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies. Two distinct electrochemical and mechanical behaviors were identified when the LCO was charged up to 4.65 V. The LCO undergoes a compressive stress generation when charged up to 4.2 V and surface fractures on the LCO particles were detected by SEM. LCO cathode experienced significantly large contractions (negative strains) when charged up to 4.65 V, where intergranular crack formation and phase transformation were detected on the LCO particles via SEM and XRD, respectively. Overall, the study bridges complicated structural deformations with in situ analysis of mechanical degradations in LCO cathodes charged at higher voltages. The correlation is vital to understanding instability mechanisms in transition metal oxides at high voltages for alkali metal ion batteries.

higher state-of-charge↗
DOE OSTI2020

Direct observation on supersonic microprojectile penetration of carbon fiber composites with ultrafast synchrotron X-ray phase contrast imaging

High-speed penetration into carbon fiber composites is of fundamental importance to materials science and impact engineering, but research along this line suffers considerably from the lack of direct experimental observations. Here we investigate such penetration dynamics of a unidirectional carbon fiber reinforced epoxy (UCFRE) composite, with a combination of in situ, ultrafast, synchrotron phase contrast imaging and finite element (FE) analysis. The experiments yield the first direct observation on projectile trajectories and fiber-scale deformation and damage in the UCFRE composites during supersonic microprojectile penetration, for different fiber orientations (0 degrees - 90 degrees from the impact direction) and projectile velocities (600 - 850 m.s -1 ), at unprecedented temporal (~ 100 ps) and spatial (5 μm) resolutions. The maximum penetration depth decreases with increasing fiber orientation angles, as a result of anisotropic damage evolution in the composite sample. Strain localizations are prone to develop along a direction perpendicular to the fiber orientation, while the damage or cavity region, along the fiber direction. FE modeling with a three-dimensional Hashin criterion yields consistent projectile trajectory and cavity morphology with the experimental results. Finally, with increasing fiber orientation angles, damage analyses show a transition in the damage mode from fiber compression to matrix compression damage, in line with the increasing maximum penetration depth.

36 MATERIALS SCIENCE↗
NASA NTRS1998

The Anatomy of the Perseus Spiral ARM: (sup 12)CO and IRAS Imaging Observations of the W3-W4-W5 Cloud Complex

Panoramic images of (sup l2)CO J = 1-0 and thermal dust emissions from the W3-W4-W5 region of the outer Galaxy are presented. These data and recently published H (sub I) 21 cm line emission images provide an approx. 1 min resolution perspective to the dynamics and thermal energy content of the interstellar gas and dust components contained within a 9 deg arc of the Perseus spiral arm. We tabulate the molecular properties of 1560 clouds identified as closed surfaces within the l-b-v CO data cube at a threshold of 0.9 K T(sup *)(sub R). Relative surface densities of the molecular (28:1) and atomic (2.5: 1) gas components determined within the arm and interarm velocity intervals demonstrate that the gas component that enters the spiral arm is predominantly atomic. Molecular clouds must necessarily condense from the compressed atomic material that enters the spiral arm and are likely short lived within the interarm regions. From the distribution of centroid velocities of clouds, we determine a random cloud-to-cloud velocity dispersion of 4 km/s over the width of the spiral arm but find no clear evidence within the molecular gas for streaming motions induced by the spiral potential. The far-infrared images are analyzed with the CO J = 1-0 and H (sub I) 21 cm line emission. The enhanced UV radiation field from members of the Cas OB6 association and embedded newborn stars provide a significant source of heating to the extended dust component within the Perseus arm relative to the quiescent cirrus regions. Much of the measured far-infrared flux (69% at 60 microns and 47% at 100 microns) originates from regions associated with star formation rather than the extended, infrared cirrus component.

Heyer, Mark H.↗
DOE OSTI2021

The mechanical response of micron-sized molecular crystals

Abstract Microstructures and corresponding properties of compacted powders ultimately depend on the mechanical response of individual particles. In principle, computational simulations can predict the results of powder compaction processes, but the selection of appropriate models for both particle–particle interactions and particle deformations across all relevant length scales remain nontrivial tasks, especially in material systems lacking detailed mechanical property information. The work presented here addresses these issues by conducting uniaxial compressions in situ inside of a scanning electron microscope to characterize the mechanical response of individual micron-sized particles of a molecular crystal, hexanitrohexaazaisowurtzitane (CL-20). This experimental approach enabled the collection of quantitative force and displacement data alongside simultaneous imaging to capture morphology changes. The results reveal information about elastic deformation, yield, plastic deformation, creep, and fracture phenomena. Accordingly, this work demonstrates a generalizable approach for assessing the mechanical response of individual micron-sized molecular crystal particles and utilizing those responses in particle-level models. Graphic abstract

36 MATERIALS SCIENCE↗
NASA NTRS1989

Impact cratering: A geologic process

The mechanisms involved in the formation of impact craters are examined theoretically, reviewing the results of recent investigations. Topics addressed include crater morphology, stress waves in solids, the contact and compression stage, the excavation stage, and ejecta deposits. Consideration is given to the scaling of crater dimensions, the crater modification stage, multiring basins, cratered landscapes, atmospheric interactions, and the implications of impact cratering for planetary evolution. Extensive diagrams, graphs, tables, and images of typical craters are provided.

Melosh, H. J.↗
NASA NTRS1991

Scalar mixing in the supersonic shear layer

Experiments were conducted in a two-stream planar mixing layer facility at convective Mach numbers of 0.28 and 0.62. Mie scattering from condensed alcohol droplets and planar laser-induced fluorescence (PLIF) of nitric oxide were used for flow visualization in both the side and plan views. The PLIF signals were approximately proportional to mixture fraction and were used to generate statistical quantities. Visualizations using both the Mie scattering and PLIF indicate the structure is essentially two-dimensional at Mc = 0.28 and three-dimensional at Mc = 0.62. Perspective renderings of side view images show the structures are streamwise ramped at Mc = 0.28 and cross-stream ramped at Mc = 0.62. This difference appears to be associated with decreasing streamwise structure spacings at the higher Mc condition. The statistical analysis suggests that with increasing compressibility, the scalar fluctuations are smaller, and the fraction of mixed fluid is higher.

Clemens, N. T.↗
NASA NTRS1993

Spatially extensive uniform stress fields on Venus inferred from radial dike swarm geometries: The Aphrodite Terra example

The high resolution and near global coverage of Magellan radar images is facilitating attempts to systematically investigate the stresses that have deformed the venusian crust. Here we continue earlier efforts to utilize approximately 170 large, radially lineated structures interpreted as dike swarms to assess the orientation of the regional maximum horizontal compressive stress (MHCS) which existed in their vicinities during emplacement. Examination of swarms near the equator reveals a link to broad scale regional structures, such as Aphrodite Terra, across distances in excess of 1000 km, suggesting the existence of first order stress fields which affect areas of more than 10(exp 6) sq km in a uniform fashion. Focusing further upon the Aphrodite Terra region, the MHCS field in the surrounding lowlands inferred from radial swarms is oriented approximately normal to the slope of the highland topography. This stress configuration appears, at a simple level, to be incompatible with that expected during either upwelling or downwelling construction of the highlands. In addition, the relatively undeformed geometry of the radial structures within the highlands implies that these dike swarm features formed more recently than their highly deformed surroundings. We conclude that the differential stresses which existed during emplacement of the dike swarms within and adjacent to the Aphrodite Terra highlands are related to the gravitational relaxation of pre-existing topography.

Grosfils, Eric B.↗
NASA NTRS1995

Alternate physical formats for storing data in HDF

Since its inception HDF has evolved to meet new demands by the scientific community to support new kinds of data and data structures, larger data sets, and larger numbers of data sets. The first generation of HDF supported simple objects and simple storage schemes. These objects were used to build more complex objects such as raster images and scientific data sets. The second generation of HDF provided alternate methods of storing data elements, making it possible to do such things as store extendible objects with in HDF, to store data externally from HDF files, and support data compression effectively. As we look to the next generation of HDF, we are considering fundamental changes to HDF, including a redefinition of the basic HDF object from a simple object to a more general, higher-level scientific data object that has certain characteristics, such as dimensionality, a more general atomic number type, and attributes. These changes suggest corresponding changes to the HDF file format itself.

Folk, Mike↗
DOE OSTI2023

INL Senior Project

What did my team set out to accomplish:? Can I put a custom Machine Learning Model on FPGA?? Can I analyze network traffic in real time?? Can a QSFP port be used with an FPGA?? Does a visual representation of the latent space enhance our understanding of network traffic?? What is QSFP QSFP (Quad Small Form-Factor Pluggable)? QSFP supports transfer speeds generally up to 100Gb/s? Runs 4 parallel lines running up to 28 Gb/s? Why the latent space is important to our project ?Latent space is the compressed mapping of data points in a non-linear fashion? Create an understanding of the relationship of data collected? Can represent that relationship of a single network packet in 3 points (X, Y, Z) Project Outline FPGA? Custom Xilinx Petalinux Image for the operating system? Python program to collect packets and run them through the DPU (Data Processing Unit)? The program then sends the information over a socket to a computer? Display Program? Python Program that collects the information sent from the FPGA and display it in a graph

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2024

Data-Efficient Dimensionality Reduction and Surrogate Modeling of High-Dimensional Stress Fields

Tensor datatypes representing field variables like stress, displacement, velocity, etc., have increasingly become a common occurrence in data-driven modeling and analysis of simulations. Numerous methods [such as convolutional neural networks (CNNs)] exist to address the meta-modeling of field data from simulations. As the complexity of the simulation increases, so does the cost of acquisition, leading to limited data scenarios. Modeling of tensor datatypes under limited data scenarios remains a hindrance for engineering applications. Here, in this article, we introduce a direct image-to-image modeling framework of convolutional autoencoders enhanced by information bottleneck loss function to tackle the tensor data types with limited data. The information bottleneck method penalizes the nuisance information in the latent space while maximizing relevant information making it robust for limited data scenarios. The entire neural network framework is further combined with robust hyperparameter optimization. We perform numerical studies to compare the predictive performance of the proposed method with a dimensionality reduction-based surrogate modeling framework on a representative linear elastic ellipsoidal void problem with uniaxial loading. The data structure focuses on the low-data regime (fewer than 100 data points) and includes the parameterized geometry of the ellipsoidal void as the input and the predicted stress field as the output. The results of the numerical studies show that the information bottleneck approach yields improved overall accuracy and more precise prediction of the extremes of the stress field. Additionally, an in-depth analysis is carried out to elucidate the information compression behavior of the proposed framework.

artificial intelligence↗
NASA NTRS1998

The Anatomy of the Perseus Spiral Arm: 12 CO and IRAS Imaging Observations of the W3-W4-W5 Cloud Complex

Panoramic images of 12CO J = 1-0 and thermal dust emissions from the W3-W4-W5 region of the outer Galaxy are presented. These data and recently published H I 21 cm line emission images provide an approximate 1' resolution perspective to the dynamics and thermal energy content of the interstellar gas and dust components contained within a 9 deg. arc of the Perseus spiral arm. We tabulate the molecular properties of 1560 clouds identified as closed surfaces within the l-b-v CO data cube at a threshold of 0.9 K T* (sub R). Relative surface densities of the molecular (28:1) and atomic (2.5:1) gas components determined within the arm and interarm velocity intervals demonstrate that the gas component that enters the spiral arm is predominantly atomic. Molecular clouds must necessarily condense from the compressed atomic material that enters the spiral arm and are likely short lived within the interarm regions. From the distribution of centroid velocities of clouds, we determine a random cloud-to-cloud velocity dispersion of 4 km s (exp. -1) over the width of the spiral arm but find no clear evidence within the molecular gas for streaming motions induced by the spiral potential. The far-infrared images are analyzed with the CO J = 1-0 and H I 21 cm line emission. The enhanced UV (Ultraviolet) radiation field from members of the Cas OB6 association and embedded newborn stars provide a significant source of heating to the extended dust component within the Perseus arm relative to the quiescent cirrus regions. Much of the measured far-infrared flux (69% at 60 micrometers and 47% at 100 micrometers) originates from regions associated with star formation rather than the extended, infrared cirrus component.

Heyer, Mark H.↗
DOE OSTI2024

Microstructural Coarsening Kinetics and Mechanical Property Changes in Long-Term Aged Sn–Pb–Sb Solder Joints

Tin-lead-antimony (50Sn–47Pb–3Sb wt.%) soldered assemblies were mechanically tested approximately 30 years after initial production and found to have solder joints of reduced strength. The microstructure of this solder alloy exhibits a ternary eutectic structure with Sn-rich, Pb-rich, and SnSb phases. Accelerated aging was performed to evaluate solder microstructural coarsening and associated strength of laboratory solder joints to correlate these properties to the “naturally aged” solder joints. Isothermal aging was conducted at room temperature, 55, 70, 100, and 135 °C and aging times that ranged from 0.1 to 365 days. The coarsening kinetics of the Pb-rich phase were determined through optical microscopy and image analysis methods established in previous studies on binary Sn–Pb solder. A kinetic equation was developed with time exponent n of 0.43 and activation energy of 24000 J/mol, suggesting grain boundary diffusion or other fast diffusion pathways controlling the microstructural evolution. Compression testing and Vickers microhardness showed significant strength loss within the first 20–30 days after soldering; then, the microstructure and mechanical properties changed more slowly over long periods of time. Further, by combining accelerated aging data and the microstructure-based kinetics, strength predictions were made that match well with the properties of the actual soldered assemblies naturally aged for 30 years. However, aging at the highest temperature of 135 °C produced anomalous behavior suggesting that extraneous aging mechanisms are active. Therefore, data obtained at this temperature or higher should not be used. Overall, the combined microstructural and mechanical property methods used in this study confirmed that the observed reduction in strength of ~ 30-year-old solder joints can be accounted for by the microstructural coarsening that takes place during long-term solid-state aging.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Probing the role of local tunnel variations in early-stage lithiation of α-MnO₂ nanowires via in situ TEM

Understanding lithium-ion transport in tunnel-structured manganese oxides is essential for designing high-performance lithium-ion battery electrode materials. Here, we elucidate the early-stage lithiation mechanism of potassium-stabilized α-MnO 2 nanowires using in situ transmission electron microscopy (TEM) coupled with electron energy-loss spectroscopy (EELS), high-resolution TEM (HRTEM), and geometric phase analysis (GPA). Real-time TEM imaging reveals clear volume expansion at the reaction front, while EELS analysis uncovers lithium-ion diffusion far beyond this region, where no visible expansion is observed, indicating fast, defect-assisted transport. GPA and HRTEM analyses show that localized tensile and compressive strain fields, originating from pre-existing local tunnel structural variations, persist after lithiation. The tensile-strained regions enable lithium-ion insertion with minimal lattice distortion, offering additional free volume that facilitates rapid lithium-ion accommodation ahead of the structural transformation. Our results demonstrate a local tunnel variation-mediated fast diffusion pathway that precedes bulk reaction, underscoring the critical role of local strain in enabling early-stage lithium transport. Given the structural versatility of MnO 2 and its ability to accommodate diverse atomic arrangements beyond the well-known tunnel phases (β-, γ-, δ-, λ-, R-phases), our findings highlight the importance of understanding and engineering local structural environments. This work provides fundamental insights into the interplay between defects, strain, and ion dynamics, and presents defect engineering as a promising approach to enhance both rate performance and structural stability in manganese-based cathodes.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Implosion simulations and optimum times of radiographic Images in OMEGA high-density-carbon cylinder experiments

The Los Alamos Ignition Threshold team is planning direct-drive cylinder implosion experiments (CylDRT24B) at the OMEGA laser, scheduled for Thursday 23 May 2024, to investigate the effect of granular microstructure in high density carbon (HDC) shells. Granular microstructure is believed to play a crucial role in seeding perturbations, reducing compression, and enhancing mix in the implosion of HDC shells at the National Ignition Facility (NIF). But the ICF community lacks a detailed understanding of how grains induce these effects, owing partly to the practical difficulty of numerically simulating the behavior of tiny nanometer-scale granular structures in laboratory-scale experiments. Our planned experiments are aimed at acquiring data to help constrain simulations and calibrate reduced models.

36 MATERIALS SCIENCE↗
NASA NTRS1998

A Substorm Triggered by a Sudden Drop in Dynamic Pressure

In traditional substorm theories the growth phase is driven by an extended period of southward IMF, which transfers large amounts of re-connected magnetic flux into the magnetotail. The subsequent substorm onset may be triggered by a northward turning of the IMF. We investigate the possibility that variations in dynamic pressure may produce these same effects for some substorms lacking a clear IMF Bz signature for both the growth phase and the onset. A sustained increase in dynamic pressure may raise the energy stored in the compressed magnetosphere system (similar to the growth phase), while a subsequent decrease in dynamic pressure may allow some of this stored energy to be released, possibly triggering a substorm. We present a global magnetospheric simulation of such a substorm, which was also imaged by the Ultraviolet Imager (UVI) on the Polar spacecraft. The plasma density rapidly doubled about 90 minutes before the substorm onset with relatively little change in the solar wind velocity and the IMF during this period. Likewise, a sudden decrease in the density almost back to the original levels occurred close to the time of substorm onset, again with no significant change in solar wind velocity or IMF, and thus this dynamic pressure drop may have triggered the substorm. We investigate whether the resulting dynamic pressure increase in the simulation produces a growth phase, a feature that is very successfully modeled by global magnetospheric simulations. We also search for the signature of substorm onset in diagnostics such as the field-aligned currents and the position of the neutral line, if any, in the magnetotail.

Elsen, R.↗
NASA NTRS2001

Comparison of MPEG-1 digital videotape with digitized sVHS videotape for quantitative echocardiographic measurements

Digital format is rapidly emerging as a preferred method for displaying and retrieving echocardiographic studies. The qualitative diagnostic accuracy of Moving Pictures Experts Group (MPEG-1) compressed digital echocardiographic studies has been previously reported. The goals of the present study were to compare quantitative measurements derived from MPEG-1 recordings with the super-VHS (sVHS) videotape clinical standard. Six reviewers performed blinded measurements from still-frame images selected from 20 echocardiographic studies that were simultaneously acquired in sVHS and MPEG-1 formats. Measurements were obtainable in 1401 (95%) of 1486 MPEG-1 variables compared with 1356 (91%) of 1486 sVHS variables (P <.001). Excellent agreement existed between MPEG-1 and sVHS 2-dimensional linear measurements (r = 0.97; MPEG-1 = 0.95[sVHS] + 1.1 mm; P <.001; Delta = 9% +/- 10%), 2-dimensional area measurements (r = 0.89), color jet areas (r = 0.87, p <.001), and Doppler velocities (r = 0.92, p <.001). Interobserver variability was similar for both sVHS and MPEG-1 readings. Our results indicate that quantitative off-line measurements from MPEG-1 digitized echocardiographic studies are feasible and comparable to those obtained from sVHS.

NASA Discipline Cardiopulmonary↗